1. Field of the Invention
The present invention relates to a method for testing a tire and a tire testing machine.
2. Description of the Related Art
Hitherto, a tire mounted on a vehicle or the like often has non-uniform circumferential portions in modulus of elasticity, dimensions, and shapes since the tire is produced by laminating various materials such as rubber, chemical fiber, and steel cord. Reactive forces of components changing periodically depending on road surfaces during high speed rotation and vibrations are generated in such non-uniform portions of the tire, and these cause degradation in traveling performance. These intended uniform performances of the tire are generally referred to as “tire uniformity”. To this end, a circumferential uniformity test is conducted on the tire by a tire testing machine after the tire is subjected to vulcanization molding. This tire testing machine tests the tire with the tire driven to rotate while pressing the outer circumference of the tire against a drum (road-surface substitute member) after fitting a bead portion on the inner circumference of the tire into a rim member, attaching the tire to rotating spindles, and then applying a predetermined internal pressure to the tire.
In the tire testing machine, a plurality of conveyers are connected to one another as tire testing conveyors for feeding a test target tire to the central position of the spindles, and the tire is fed to the central position of the spindles in a state in which the tire lies on its side. Note that there is also known a tire testing machine configured to attach the tire to the spindles in a state of standing up with the spindles lying on its side.
Hitherto, the tire testing machine tests the tire by, after securing the tire by chucks, accelerating the rotation of the tire to reach a specified rotational speed (60 rpm for the uniformity test), rotating the tire at the specified rotational speed, and contacting the drum with the tire that rotates at the specified rotational speed. However, the conventional tire testing method and tire testing machine have the following problems. Since the drum is made to contact the rotating tire and the drum rotates to follow the rotation of the tire, a slip occurs between the tire and the drum and the surface of the drum scrapes off that of the tire at a time of the initial rotation of the drum. As a result, the surface of the drum is disadvantageously contaminated with tire rubber at an early time.
To prevent the early contamination of the drum, a tire testing machine disclosed in U.S. Pat. No. 6,016,695 tests a tire by, after securing the tire by chucks, contacting a drum with the tire in a stationary state and accelerating the rotation of the tire to increase the rotational speed of the tire to a specified rotational speed for the test.